Permeability of arterial endothelium to plasma macromolecules: The concomitant transfer of plasma phosphatidylethanolamine, phosphatidylcholine, sphingomyelin and phosphoprotein across the aortic endothelial surface in normal cockerels following the injection of labelled, hyperlipidemic, plasma With a note on carbon monoxide

Abstract

An in vivo model system for the study of plasma lipoprotein flux into arterial intima-media has been characterized as follows. Native, whole plasma from stilbestrol-treated, hyperlipidemic cockerels, which received [ 32P]orthophosphate 24 h prior to exsanguination, was injected intravenously into normal recipient cockerels from which aortic intima-media layers were prepared 0.12, 1, 5 and 10 h later. For at least 5 h it was seemingly possible to identify the [ 32P] phosphoprotein influx to intima—media across the intimal endothelium with simple intima-media uptake values, i.e. efflux was not noticeable. The same applies to the labelled phospholipids. Omitting results from experiments of 10 h duration the average intimal plasma clearance values for phosphoprotein ranged from 0.030 to 0.260 ml cm −2 h −1, with an average value of 0.137 μl cm −2 h −1. For phosphatidylethanolamine and phosphatidylcholine, the ranges were from 0.020 to 0.200 and from 0.020 to 0.180, respectively, with the same average value of 0.083 μl cm −2 h −1. The clearance for sphingomyelin did not differ significantly from the clearances for the two other phospholipids studied. The mean molecular weight (MW) for the very low density lipoprotein which carries by far the greater part of the phospholipids in plasma from estrogenized birds was estimated to be about 3–4 × 10 6. The phosphoprotein complex present in this plasma showed for the greater part a MW of about 8 × 10 5. The lipoprotein flux was not measurably influenced by exposure of the birds to 200 ppm of carbon monoxide.